It is well known in motor vehicles to provide an air bag module mounted to a steering wheel. The air bag module typically includes an inflator for generating gas to inflate an air bag for restraining an occupant. The air bag module also typically includes an air bag cover which houses the air bag and inflator. The cover includes weakened portions which break open upon air bag deployment.
It is known to provide an air bag cover molded of a resilient plastic material. It is also known to mount membrane horn switches on a backing plate which is mounted in spaced relation to the cover. These membrane horn switches conventionally comprise two very thin sheets having conductive coatings which are normally separated by thin spacers. Pressure on the switch presses the conductive surfaces together to close a circuit and actuate a horn. Typical membrane horn switches are less than one millimeter in thickness. To actuate the horn, the driver must sufficiently compress the cover directly above the switch to apply pressure to the membrane horn switch for actuating the horn.
In the prior art, the backing plate is typically planar and the membrane horn switch is fixedly mounted to the backing plate, such as by an adhesive. Alternately, the backing plate and the membrane horn switch may each have aligned apertures through which plastic offset posts of the cover extend to fixedly fasten both the backing plate and the membrane horn switch to the cover, such as by heat staking or other bonding processes. Once the membrane horn switch and backing plate are attached to the cover, the membrane horn switch cannot be removed for servicing without damaging of the backing plate, cover and membrane horn switch. Thus, an entire new cover and backing plate are also required each time the membrane horn switch is serviced.